I can answer some of your questions. I have a 19 yr old DD who is 5 feet tall and 85 pounds (I told her to stop growing when she was about 14 because she was the perfect size and for once, she listened to me).
Anyway, she has cerebral palsy and is classified as mixed, predominently spastic quad. She is able to stand with full support and can do a pivot transfer, but in the interest of speed getting her on, we usually do lift her. The CMs (cast members) are not allowed to lift or physically transfer anyone. They can do things like holding the wheelchair steady or moving out of the way after the person is out.
Part of whether he would be safe on rides or not depends on his ability to keep at least a bit of balance sitting up. My DD has a lot of extensor tone, so when she is excited, she tends to stiffen and straighten up; this kind of causes her to either be sitting on her back (instead of her butt) or hold her back straight and be partly stand up. But, she has pretty fair sitting balance and head control when out of her wheelchair. You really need both of those things for most of the "wild rides". Most do not have any head/neck support and many rides have hard plastic seats that can be fairly slippery.
If you go to the FAQs on Disabilities on the top of this board, you will find links to the WDW Guidebooks for Guests with Disabilties. They don't give a lot of info about the rides, but do have a list of rides/attractions where wheelchair users can stay in the wheelchair for the entire attraction. This will be important for you. Making a lot of transders is very tiring, especially at a park like MK where it seems like you just got settled and the ride is over and it's time to get off. We alternate rides with wheelchair cars and those that require a transfer to avoid wearing ourselves out.
DD likes wild rides and, at one time or another, has been on everything except Space Mountain, Thunder Mountain Railroad, Rock N Roller Coaster, Astro Orbiter (in Tomorrowland in MK) and Mission Space. Space Mountain and Rock N Roller Coaster would not work at all for our situation. You ride one in front of the other in single seats, so we decided that would not be a safe ride for her. They both have harnesses that go over the shoulders.
She has not been on Mission Space, so I can't give any advice specifically about wheelchair access, but DH has been on it several times without DD and he could see no problems (he's our chief child-lifter and is pretty good at assessing what would work or not work). There are individual seats with seat belts.
DD was on Tower of Terror and loved it. The last time we went on with her, they had only a lap bar that went across the whole row. Since then, they have changed to individual seat belts. I believe that would work better. The problem we had was that she extended and stood almost up. It was not so bad though that we would not go on again. You do need to be aware though that the ride has bench seats without much back support.
Rides that I would definately suggest not going on:
- Primevel Whirl at AK. It's a sort of tame roller coaster that also spins around like the teacups. The combination of the two motions made it very difficult for my DD to sit up and caused her to end the ride nearly sitting on the floor or the ride car with the seat belt around her chest instead of at her waist.
- Peter Pan's Flight at MK. The ride is not so difficult to get into, but there is a moving walkway to get on and off. This is the one ride where the moving walkway can't be slowed of stopped, so you have a limited amount of time and space to get in and out. The last time we rode, my DD almost ran out of space carrying DD off (which would have run them smack into a wall). The moving walkway can be stopped only in an emergency (which I guess the CM didn't think almost runing into a wall was, since they didn't stop the ride for DH).
Some othe "wild rides" that might work:
- Star Tours at the Studio. It has individual seats with seat belts. The wheelchair can be driven into the ride care (it's like a theater, where the whole theater is a simulator). The transfer would be like transferring to a car seat. After getting into the seat, the CM takes the wheelchair away and brings it back to you once the ride is finished. There is an individual seat belt, but I would strongly recommend asking the CM for the 4 point harness. I attaches to the seat to help hold the shoulders in place and helps a lot to avoid being thrown around.
- Body Tours (in The Wonders of Life in Epcot) has a similar set up to Star Tours. The Wonders of Life has been closed recently (the pavilion lost its sponsor), so the ride may not be open when you are there. The Wonders of Life is supposed to be open "seasonally", but it was closed in last January, March and July when my family was at WDW.
- Test Track at Epcot. The regular wheelchair boarding area has the car below you and you need to step down into it to get in and up to get out. But, there is an alternate wheelchair boarding area where the ride car is in a higher position. The restraint for that ride is a seat belt. You can request a bar that goes next to the person with a disability. I think it's actually a grab bar for getting in, but we find it helps to keep DD in place while on the ride. It does require a lot of our assistance for DD to keep from extending on this ride.
